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Facebook Chairman and CEO Mark Zuckerberg (first row, second from right) applauds at the opening bell of the Nasdaq stock market Friday from Facebook headquarters in Menlo Park, Calif. The Facebook IPO fell flat, with shares at the close only 23 cents above their opening price of $38. But the company's best days lay ahead.

So the Facebook IPO finally took place and Facebook shares are now available for all and sundry – worth at the end of their first day of trading almost exactly what they were worth at the beginning: about $38 apiece.

Now the next difficult question: Is Facebook the next Apple, Google, or Microsoft – that triumvirate of companies that we tend to come across one way or another in our daily dealings, or which have in some way or other driven how we experience the Web today? (You might not own an Apple device, but if you've used a smartphone recently then it probably had a touch-screen-driven system, and apps, and you might have thought about buying music from an online store.)

So is Facebook going to drive our Web experience forward in the way that those three have? In researching and writing my book "Digital Wars," on how those three companies have interacted down the years, a few points became clear to me.

First, if you get it right, then controlling the software platform can make you very rich. Microsoft owns Windows and Office, and together they actually contribute about 105 percent of its profits every quarter (other divisions, notably search, then make a loss, bringing us back to 100 percent).

Equally, you have to have the right way of making money from that software. Apple owns iOS and Mac OSX, its mobile and desktop operating systems, and because it also controls the hardware, it can rake in colossal amounts of money. But when it briefly tried licensing the Mac OS back in the 1990s, it nearly killed the company, because the ecosystem was too small. So you need breadth – in effect, a broad monopoly – for a software platform to be viable.

The next lesson is that Web companies are very vulnerable to disruption. Google in 1998 (when my book opens) was just an upstart, a company that thought it had a better way to search. But many people thought then that search was solved; Yahoo turned down Google's search algorithm because it was too good, which would mean too few people would look at the pages where it sold ads. Google zoomed past Yahoo within a few years.

What also helps: getting embedded into the public consciousness. The first use of "Google" as a verb that I could find in a newspaper was in January 2001; by February 2003 it was being mentioned in passing in an episode of ER, then the biggest show on TV. Nobody has ever, ever used any of the various names for Microsoft's search engine as a verb. Everyone knows what you mean by "Googling" something. That's pretty hard to dislodge.

Finally: It really helps to have a strong, driven leader who feels deeply involved in the company's fate. Apple benefited hugely from Steve Jobs returning in 1996/7; he felt that what happened to Apple reflected deeply on him, and to some extent he couldn't separate himself from it. Bill Gateswas Microsoft, for quite a lot of its life: a hard-driving, detail-crunching, incredibly smart businessman. Google's founders, Larry Page and Sergey Brin, have made many of the key decisions (such as buying the mobile company Android in 2005, without even referring to their then-chief executive Eric Schmidt).

Working backwards: Facebook chief executive Mark Zuckerberg is deeply committed to it. He is not doing Facebook as a side project; he's not in it to cash out, because he could have done that years ago. This is his life's work, and he is clearly going to try to make it the biggest company it can possibly be.

Next, the site's name has entered the language. Pretty much everyone in the West knows what Facebook is, and essentially what it's for, even if they don't use it. There is a vast group of people who have never heard of it, mostly in Asia and Africa, and many countries where it is not the biggest social network – particularly China. But having become embedded in our language, it won't go away quickly.

Third, how vulnerable is it to disruption? We can cite Friends Reunited in the United Kingdom (which got old school friends together), Bebo, and of course MySpace as once-giant social networks that are now rotting hulks moored off the shores of the Web, just waiting to be broken up. But a key difference about them: They were bought by bigger corporations. Quite possibly Facebook would be facing the same fate if it had acceded to one of those takeover offers, because corporations struggle badly with the idea of acquiring a company that becomes bigger than the parent; they naturally try to rein it in, or absorb it, and that kills the spark.

Even so, the question everyone has is whether "some other social network" will come along and take away Facebook's unique selling proposition. Google is certainly trying its best with its Google+ network, but there's little sign that people are engaged with it. Facebook has the heft to push aside many others.

The toughest challenge in terms of disruption is the shift to mobile. Born in 2004, Facebook effectively predates the mobile Internet, which only began to take off in 2007. That means its DNA isn't adapted – yet? – to being viewed on a four-inch screen. That's a tough challenge, and one that all the older Web companies – notably Google and Yahoo – are struggling with. This will either be the growth limit for Facebook, or its rocket booster. But recall what I said above about Mr. Zuckerberg. Mr. Jobs was able to pilot Apple into the world of mobility (iPod sales quickly outstripped Mac sales, and iPhone quarterly revenues alone now exceed Microsoft's total). Facebook knows it has a huge shift to make.

And lastly, controlling the platform. Once more, Zuckerberg has seen that it's better to own the playing field and hire it out to all comers than to wall it off and charge an entrance fee. He's turned Facebook into a platform that is spreading all across the Web (through Like buttons, apps, commenting systems, and more). And we all know its name.

So for all those reasons, I think Facebook's best days still lie ahead of it. Note that I'm not making any recommendation about whether the shares are worth buying or good value; that's entirely up to you to decide. (I don't own or directly control any shares in any company, and have no intention of changing that.) This is just the bridge to the next stage.